1. Field of the Invention
The invention pertains to guidance systems for agricultural machines and, more particularly, to an optical guidance system for directing the lateral movement of an agricultural machine relative to a severed edge of the crop material or relative to a windrow of crop previously severed.
2. Description of the Prior Art
The field operation of an agricultural harvesting machine is a tedious process that is tiring to the human operator. For efficient operation it is necessary that the machine be directed such that the header engages the maximum amount of crop without leaving any standing crop. Studies have shown that more than half of the operator's attention capacity is engaged in guiding the harvesting machine along the crop edge to attain the maximum intake. After many hours in the field, the operator's responses often deteriorate resulting in large steering errors thereby lessening the intake or leaving patches of crop unsevered. Accordingly, providing a guidance assist on the harvesting machine lessens the tedium, permits more accurate steering control over longer working days and maintains maximum intake while harvesting.
Guidance of the harvesting machine at present relies on the operator's visual perception of the crop edge. This implies the existence of a contrast discriminant between the severed and unsevered crop material which is perceived by the operator and from which he steers the machine. A system which relies primarily on amplitude measurements of the reflected illuminations from the severed and unsevered portions of the crop would obviously be prone to numerous errors due to the great variations in the reflected illumination. However, the system of the present invention makes use of the fact that a contrast discriminant does exist and attends to by locating the relative position of the discrimination in an optical scan of the crop.
Automatic steering systems for harvesters are known in the art, such as, U.S. Pat. No. 3,946,825 which issued to Josef Gail on Mar. 30, 1976 and British patent specification No. 1,371,276, however, such known systems involve sensing means disposed on a boom extending from the machine for contacting or contactless sensing of the crop. Specifically, the contactless sensing refers to an emitter and a receiver for sensing the crop material. The limitations, however, of a sensor disposed on a boom or arm extending from the vehicle and of a luminous transmitter under various lighting conditions for accurate steering are apparent.